Load cells of the general type defined above are known in the art. One example is shown and described in EP-A-402 261. This load cell device has a plate-shaped chamber, which is filled with liquid but equally well could be filled with a silicon rubber disc or the like for transmitting a force to a piston of a pneumatic valve device for delivering a pneumatic signal depending on the force exerted on the liquid or disc. The internal arrangement of the device for exerting a compression force on the liquid or disc irrespective of whether the external force is pushing or pulling is comparatively complex and accordingly expensive and sensitive to disturbances.
Another similar device for measuring an axial force in either direction in a shaft is shown in EP-A-373 334, but here two separate elastic elements and pressure responsive devices (pressure transducers) are utilized for the two force directions, which is a complication.
A load cell of the type concerned may be used in many applications where a signal depending on a load or force is desirable, and no limitation of the present invention in this respect is intended.
However, the main purpose for the load cell according to the invention is to transmit a signal depending on the tangential brake force obtained in a brake arrangement, preferably at a rail vehicle, so that the brake force applied may be continuously or intermittently adopted to obtain a desired brake characteristic. In this way a feedback control system can be attained, which is of growing importance at modern rail vehicles.